1. Field
The disclosure relates to a method, system, and article of manufacture for redirecting storage access requests.
2. Background
A host server may continue to perform data access operations to a backup or secondary storage controller in the event of a failure of a primary storage controller. For example, in IBM* HyperSwap* configurations a host server may access a primary and a secondary storage controller. The host server may direct all storage accesses to the primary storage controller and the two storage controllers may operate in concert to ensure that identical data is saved in both. HyperSwap software on the host server may be able to determine when the primary storage controller has failed and can automatically redirect all storage accesses to the secondary storage controller. *IBM, ESCON, HyperSwap, TotalStorage, and OS/390 are trademarks or registered trademarks of International Business Machines Corporation.
The primary and secondary storage controllers may use a Peer-to-Peer Remote Copy (PPRC) function to copy data from the primary storage controller to the secondary storage controller. In the synchronous type of operation for PPRC, i.e., synchronous PPRC, the updates done by a host application to the local storage volumes at the primary storage controller are synchronously shadowed onto the remote storage volumes at the secondary storage controller. As synchronous PPRC is a synchronous copying solution, write updates are ensured on both copies (local and remote storage volumes) before the write is considered to be completed for the host application. In synchronous PPRC the host application does not get the “write complete” condition until the update is synchronously done in both the local and the remote volumes. Therefore, from the perspective of the host application on the host server the data at the remote volumes at the secondary storage controller is equivalent to the data at the local volumes at the primary storage controller, and a failed primary storage controller can be substituted by the secondary storage controller.